scholarly journals Shear thickening of a non-colloidal suspension with a viscoelastic matrix

2019 ◽  
Vol 880 ◽  
pp. 1070-1094 ◽  
Author(s):  
Adolfo Vázquez-Quesada ◽  
Pep Español ◽  
Roger I. Tanner ◽  
Marco Ellero
Keyword(s):  
Experimental Data ◽  
Volume Fraction ◽  
Colloidal Suspension ◽  
Solid Volume Fraction ◽  
Microstructural Analysis ◽  
Three Dimensional ◽  
Shear Thickening ◽  
Dissipation Function ◽  
Spherical Particles ◽  
Viscoelastic Matrix

We study the rheology of a non-colloidal suspension of rigid spherical particles interacting with a viscoelastic matrix. Three-dimensional numerical simulations under shear flow are performed using the smoothed particle hydrodynamics method and compared with experimental data available in the literature using different constant-viscosity elastic Boger fluids. The rheological properties of the Boger matrices are matched in simulation under viscometric flow conditions. Suspension rheology under dilute to semi-concentrated conditions (i.e. up to solid volume fraction $\unicode[STIX]{x1D719}=0.3$) is explored. It is found that at small Deborah numbers $De$ (based on the macroscopic imposed shear rate), relative suspension viscosities $\unicode[STIX]{x1D702}_{r}$ exhibit a plateau at every concentration investigated. By increasing $De$, shear thickening is observed, which is related to the extensional thickening of the underlying viscoelastic matrix. Under dilute conditions ($\unicode[STIX]{x1D719}=0.05$), numerical results for $\unicode[STIX]{x1D702}_{r}$ agree quantitatively with experimental data in both the $De$ and $\unicode[STIX]{x1D719}$ dependences. Even under dilute conditions, simulations of full many-particle systems with no a priori specification of their spatial distribution need to be considered to recover precisely experimental values. By increasing the solid volume fraction towards $\unicode[STIX]{x1D719}=0.3$, despite the fact that the trend is well captured, the agreement remains qualitative with discrepancies arising in the absolute values of $\unicode[STIX]{x1D702}_{r}$ obtained from simulations and experiments but also with large deviations existing among different experiments. With regard to the specific mechanism of elastic thickening, the microstructural analysis shows that elastic thickening correlates well with the average viscoelastic dissipation function $\unicode[STIX]{x1D703}^{elast}$, requiring a scaling as $\langle \unicode[STIX]{x1D703}^{elast}\rangle \sim De^{\unicode[STIX]{x1D6FC}}$ with $\unicode[STIX]{x1D6FC}\geqslant 2$ to take place. Locally, despite the fact that regions of large polymer stretching (and viscoelastic dissipation) can occur everywhere in the domain, flow regions uniquely responsible for the elastic thickening are well correlated to areas with significant extensional component.

Dispersion of solids in fracturing flows of yield stress fluids

2017 ◽  
Vol 830 ◽  
pp. 93-137 ◽  
Author(s):  
S. Hormozi ◽  
I. A. Frigaard
Keyword(s):  
Yield Stress ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Process Variations ◽  
Model Framework ◽  
Shear Rates ◽  
Low Viscosity ◽  
High Shear Rates ◽  
Solids Concentration

Solids dispersion is an important part of hydraulic fracturing, both in helping to understand phenomena such as tip screen-out and spreading of the pad, and in new process variations such as cyclic pumping of proppant. Whereas many frac fluids have low viscosity, e.g. slickwater, others transport proppant through increased viscosity. In this context, one method for influencing both dispersion and solids-carrying capacity is to use a yield stress fluid as the frac fluid. We propose a model framework for this scenario and analyse one of the simplifications. A key effect of including a yield stress is to focus high shear rates near the fracture walls. In typical fracturing flows this results in a large variation in shear rates across the fracture. In using shear-thinning viscous frac fluids, flows may vary significantly on the particle scale, from Stokesian behaviour to inertial behaviour across the width of the fracture. Equally, according to the flow rates, Hele-Shaw style models give way at higher Reynolds number to those in which inertia must be considered. We develop a model framework able to include this range of flows, while still representing a significant simplification over fully three-dimensional computations. In relatively straight fractures and for fluids of moderate rheology, this simplifies into a one-dimensional model that predicts the solids concentration along a streamline within the fracture. We use this model to make estimates of the streamwise dispersion in various relevant scenarios. This model framework also predicts the transverse distributions of the solid volume fraction and velocity profiles as well as their evolutions along the flow part.

Fluid flow and heat transfer of a stratified system during natural convection – influence of chamfered corners

2019 ◽  
Vol 29 (2) ◽  
pp. 470-486 ◽  
Author(s):  
Alireza Rahimi ◽  
Aravindhan Surendar ◽  
Aygul Z. Ibatova ◽  
Abbas Kasaeipoor ◽  
Emad Hasani Malekshah
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Entropy Generation ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Immiscible Fluids ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose This paper aims to investigate the three-dimensional natural convection and entropy generation in the rectangular cuboid cavities included by chamfered triangular partition made by polypropylene. Design/methodology/approach The enclosure is filled by multi-walled carbon nanotubes (MWCNTs)-H2O nanofluid and air as two immiscible fluids. The finite volume approach is used for computation. The fluid flow and heat transfer are considered with combination of local entropy generation due to fluid friction and heat transfer. Moreover, a numerical method is developed based on three-dimensional solution of Navier–Stokes equations. Findings Effects of side ratio of triangular partitions (SR = 0.5, 1 and 2), Rayleigh number (103 < Ra < 105) and solid volume fraction (f = 0.002, 0.004 and 0.01 Vol.%) of nanofluid are investigated on both natural convection characteristic and volumetric entropy generation. The results show that the partitions can be a suitable method to control fluid flow and energy consumption, and three-dimensional solutions renders more accurate results. Originality/value The originality of this work is to study the three-dimensional natural convection and entropy generation of a stratified system.

scholarly journals Interface-resolved simulations of particle suspensions in Newtonian, shear thinning and shear thickening carrier fluids

2018 ◽  
Vol 852 ◽  
pp. 329-357 ◽  
Author(s):  
Dhiya Alghalibi ◽  
Iman Lashgari ◽  
Luca Brandt ◽  
Sarah Hormozi
Keyword(s):  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Shear Thickening ◽  
Fluid Phase ◽  
Local Strain ◽  
Reynolds Numbers ◽  
Mean Value ◽  
Strain Rates ◽  
Local Shear ◽  
The Mean

We present a numerical study of non-colloidal spherical and rigid particles suspended in Newtonian, shear thinning and shear thickening fluids employing an immersed boundary method. We consider a linear Couette configuration to explore a wide range of solid volume fractions ($0.1\leqslant \unicode[STIX]{x1D6F7}\leqslant 0.4$) and particle Reynolds numbers ($0.1\leqslant Re_{p}\leqslant 10$). We report the distribution of solid and fluid phase velocity and solid volume fraction and show that close to the boundaries inertial effects result in a significant slip velocity between the solid and fluid phase. The local solid volume fraction profiles indicate particle layering close to the walls, which increases with the nominal $\unicode[STIX]{x1D6F7}$. This feature is associated with the confinement effects. We calculate the probability density function of local strain rates and compare the latter’s mean value with the values estimated from the homogenisation theory of Chateau et al. (J. Rheol., vol. 52, 2008, pp. 489–506), indicating a reasonable agreement in the Stokesian regime. Both the mean value and standard deviation of the local strain rates increase primarily with the solid volume fraction and secondarily with the $Re_{p}$. The wide spectrum of the local shear rate and its dependency on $\unicode[STIX]{x1D6F7}$ and $Re_{p}$ point to the deficiencies of the mean value of the local shear rates in estimating the rheology of these non-colloidal complex suspensions. Finally, we show that in the presence of inertia, the effective viscosity of these non-colloidal suspensions deviates from that of Stokesian suspensions. We discuss how inertia affects the microstructure and provide a scaling argument to give a closure for the suspension shear stress for both Newtonian and power-law suspending fluids. The stress closure is valid for moderate particle Reynolds numbers, $O(Re_{p})\sim 10$.

Rheological Behavior of Semisolid Al-6.5wt%Si Alloy under Cyclic Shear Deformation

2011 ◽  
Vol 306-307 ◽  
pp. 104-107
Author(s):  
Hong Chao Luo ◽  
Jun Mei Yang ◽  
Li Yuan Sun ◽  
Li Ping Ju
Keyword(s):  
Experimental Data ◽  
Shear Rate ◽  
Hysteresis Loop ◽  
Shear Deformation ◽  
Rheological Behavior ◽  
Qualitative Agreement ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Cyclic Shear ◽  
The Difference

In the present work, the MCF model for semisolid metal slurries (SSMS) is applied to investigate the thixotropy of the Al-6.5wt%Si alloy under cyclic shear deformation. The study shows that the semisolid Al-6.5wt%Si alloy has the behavior of thixotropy. The area of the hysteresis loop increases with decreasing the up-time, the initial shear rate and increasing resting time, solid volume fraction and maximum shear rate, respectively. These results have qualitative agreement with the experimental data. The origin of the hysteresis loop is atrributed to the difference between the deagglomeration rate and the agglomeration rate.

Rheological Behaviors of Alumina Aqueous Suspensions

2007 ◽  
Vol 280-283 ◽  
pp. 1039-1040
Author(s):  
Tie Chao Wang ◽  
Jin Long Yang ◽  
Li Guo Ma ◽  
Yong Huang
Keyword(s):  
Volume Fraction ◽  
Aqueous Suspension ◽  
Solid Volume Fraction ◽  
Shear Thickening ◽  
Shear Thinning ◽  
Critical Value ◽  
Rheological Behaviors ◽  
Aqueous Suspensions ◽  
Alumina Suspensions

Rheological behaviors of alumina aqueous suspension were investigated, and some methods to modify the rheological behaviors of the suspensions were studied. It was found that there is a critical solid volume fraction for alumina aqueous suspensions. When the volume fraction reaches or exceeds the critical value the suspensions show shear thinning behaviors all along, while above which the rheological behaviors of alumina suspensions change from shear thinning to shear thickening.

Three-Dimensional Printed Dielectric Substrates for Radio Frequency Applications

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Vana Snigdha Tummala ◽  
Ahsan Mian ◽  
Nowrin H. Chamok ◽  
Dhruva Poduval ◽  
Mohammod Ali ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Acrylonitrile Butadiene Styrene ◽  
Volume Fractions ◽  
The Core ◽  
Sandwich Construction ◽  
3D Printed ◽  
Rf Antenna

Engineered porous structures are being used in many applications including aerospace, electronics, biomedical, and others. The objective of this paper is to study the effect of three-dimensional (3D)-printed porous microstructure on the dielectric characteristics for radio frequency (RF) antenna applications. In this study, a sandwich construction made of a porous acrylonitrile butadiene styrene (ABS) thermoplastic core between two solid face sheets has been investigated. The porosity of the core structure has been varied by changing the fill densities or percent solid volume fractions in the 3D printer. Three separate sets of samples with dimensions of 50 mm × 50 mm × 5 mm are created at three different machine preset fill densities each using LulzBot and Stratasys dimension 3D printers. The printed samples are examined using a 3D X-ray microscope to understand pore distribution within the core region and uniformity of solid volumes. The nondestructively acquired 3D microscopy images are then postprocessed to measure actual solid volume fractions within the samples. This measurement is important specifically for dimension-printed samples as the printer cannot be set for any specific fill density. The experimentally measured solid volume fractions are found to be different from the factory preset values for samples prepared using LulzBot printer. It is also observed that the resonant frequency for samples created using both the printers decreases with an increase in solid volume fraction, which is intuitively correct. The results clearly demonstrate the ability to control the dielectric properties of 3D-printed structures based on prescribed fill density.

scholarly journals Experimental analysis of particle clustering in moderately dense gas–solid flow

2021 ◽  
Vol 933 ◽  
Author(s):  
Kee Onn Fong ◽  
Filippo Coletti
Keyword(s):  
High Speed ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Stokes Number ◽  
Spherical Particles ◽  
High Speed Imaging ◽  
Dense Particle ◽  
Laboratory Observation ◽  
Laboratory Setup ◽  
Wide Range

In collisional gas–solid flows, dense particle clusters are often observed that greatly affect the transport properties of the mixture. The characterisation and prediction of this phenomenon are challenging due to limited optical access, the wide range of scales involved and the interplay of different mechanisms. Here, we consider a laboratory setup in which particles fall against upward-moving air in a square vertical duct: a classic configuration in riser reactors. The use of non-cohesive, monodispersed, spherical particles and the ability to independently vary the solid volume fraction ( $\varPhi _V = 0.1\,\% - 0.8\,\%$ ) and the bulk airflow Reynolds number ( $Re_{bulk} = 300 - 1200$ ) allows us to isolate key elements of the multiphase dynamics, providing the first laboratory observation of cluster-induced turbulence. Above a threshold $\varPhi _V$ , the system exhibits intense fluctuations of concentration and velocity, as measured by high-speed imaging via a backlighting technique which returns optically depth-averaged fields. The space–time autocorrelations reveal dense and persistent mesoscale structures falling faster than the surrounding particles and trailing long wakes. These are shown to be the statistical footprints of visually observed clusters, mostly found in the vicinity of the walls. They are identified via a percolation analysis, tracked in time, and characterised in terms of size, shape, location and velocity. Larger clusters are denser, longer-lived and have greater descent velocity. At the present particle Stokes number, the threshold $\varPhi _V \sim 0.5$ % (largely independent from $Re_{bulk}$ ) is consistent with the view that clusters appear when the typical interval between successive collisions is shorter than the particle response time.

scholarly journals Progress on numerical simulation of nanofluids: impact of an isothermal spherical partition on the mixed convection of nanofluids within cubic enclosures

2020 ◽  
Vol 307 ◽  
pp. 01016
Author(s):  
A. BOUTRA ◽  
K. RAGUI ◽  
N. LABSI ◽  
Y.K. BENKAHLA ◽  
R BENNACER
Keyword(s):  
Lattice Boltzmann ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Numerical Code ◽  
Three Dimensional Flow ◽  
Boltzmann Method ◽  
Do So

The main objective of our work is to light out the three-dimensional flow of an Ag-water nanofluid within a lid-driven cubical space which equipped with a spherical heater into its center. Due to its crucial role in the characterization of the main transfer within such configurations, impact of some parameters is widely inspected. It consists the Richardson value (0,05 to 50), the solid volume fraction (0% to 10%), as well as the heater geometry (10% ≤ d ≤ 25%). To do so, a numerical code based on the Lattice-Boltzmann method, coupled with a finite difference one, is used. The latter has been validated after comparison between the present results and those of the literature. It is to note that the three dimensions D3Q19 model is adopted based on a cubic Lattice, where each pattern of the latter is characterized by nineteen discrete speeds.

Squeeze Casting of Semi-Solid A356 Alloy

2014 ◽  
Vol 217-218 ◽  
pp. 436-441
Author(s):  
Xiang Jie Yang ◽  
Ming Wang ◽  
Liang Sheng Ding ◽  
Hong Min Guo ◽  
Xu Bo Liu
Keyword(s):  
Cross Section ◽  
Squeeze Casting ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Three Dimensional ◽  
A356 Alloy ◽  
Equivalent Diameter ◽  
Squeeze Cast ◽  
Cast Product ◽  
Semi Solid

the rheo-squeeze casting (Rheo-SQC) combining the rheocasting and the SQC was developed, in which semi-solid slurry was produced by the low superheat pouring with a shearing field (LSPSF) process. The three dimensional morphology of the primary α-Al phase and the rest spacing of slurry prepared by LSPSF process have been reconstructed and visualized, and the microstructures of squeeze cast A356 alloy have been obtained. Based on the three dimensional microstructure reconstructed, their three dimensional characterizations such as solid volume fraction, equivalent diameter of the extracted primary α-Al phase were measured and calculated, and the microstructures of cross section of squeeze cast product were investigated.

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